Precision sharpening of hunting style knives and certain Asian knives in knife sharpeners has historically been limited because of imprecise control of the angle of the blade's cutting edge facet as presented to the moving abrasive.
Commonly in sharpeners to control the sharpening angle, the face of the hunting knife is laid on a planar angle guide surface and held there by hand, by a magnet or a spring. Because of the complex geometric design of the face of hunting and certain Asian knife blades the positioning of these style blades on such angle guides is unstable and ambiguous, consequently precise angular control of the facets being ground at the knife edge is seriously compromised.